A cooling system in which oil circulated by an electric oil pump is used as a refrigerant, for example, a cooling system installed in a vehicle with an idle stop function and has a configuration that continues to supply oil to a start clutch and a continuously variable transmission and the like during an idle stop is known (See, for example, Patent Document 1).
As shown in FIG. 16, the cooling system is so configured to drive the electric oil pump 55 with the motor 54 to supply the oil in the oil pan 56 to the device 57 to be cooled, thereby cooling the start clutch and the continuously variable transmission that constitute the device 57 to be cooled (See paragraphs 0014, 0015 and FIG. 1).
In this cooling system, the electric oil pump 55 serves as a hydraulic pressure source for the transmission of the idle stop system, and an accurate flow rate control is required. Therefore, in the control unit 50, the motor control unit 52 sets the drive duty based on the motor rotation speed fed back from the motor 54, and the motor drive unit 53 drives the motor 54 based on the drive duty.
Further, the failure detection unit 51 determines the light load abnormality such as a decrease in the amount of oil in the oil pan 56, oil leakage from the hydraulic system piping, idling of the electric oil pump 55, and the like, based on the phase current (current), the rotation speed, and the temperature (oil temperature) of the oil (oil) detected by the temperature sensor 58.